Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
Geothermal Energy in the 21st Century: What Engineers & Scientists Need to Know
Stuart Simmons Energy & Geoscience Institute, University of Utah
Tinguiririca geothermal prospect, central Chile, 3400 m asl
Geothermal energy (heat from the Earth’s interior) is utilized for thermal energy and electrical energy production.
The resource is huge but low grade; the best/hottest resources are localized, dependent on geology.
Conventional hydrothermal resources have been in production for ~100 yrs; but long payback period + financial risks due to uncertainty in fluid flow systems & resource assessment.
Unconventional resources EGS-type resources are difficult to develop; i.e., how do you produce energy from a large volume (100-500 km3), hot “dry” rock at 3-5 km depth?
DOE FORGE represents new, big R&D support for an EGS field laboratory; new opportunity for advancing novel technologies. Utah test site is being proposed.
Summary
Why use geothermal energy? Strengths
Clean, renewable energy Base load generation Low cost to maintain Climate/weather independent Reliable
Weaknesses Long lead time: concept to production Large entry barriers High upfront costs/risks Cannot be stored/exported Location controlled by geology
Commercial considerations
Resource information Managing risks & costs Electicity generation
Location with respect to grid & market Availability of skilled personnel Direct use
Efficient use of geothermal energy involves direct heating applications
Diverse Nature of Geothermal Resources
Moore & Sim
mons, Science, 2013
Total Installed Electricity Generation ~11-12 GWe
111 MW power station 12 Hectares of glass house
power station well head
glass house tomatoes for export
Mokai: parallel development of high & low enthalpy resource use
Taupo Volcanic Zone, North Island, New Zealand
Power Cycles & Electricity Generation
liquid-dominated reservoir
vapor-dominated reservoir
liquid-dominated reservoir
condensing turbines binary plant G
raph
ics:
Duf
field
& S
ass,
200
3
>200° C ~240° C <200° C
Wairakei 2010 ~235 MW capacity 1729 GWh of net generation 54.6 million tonnes geothermal fluid 60.8 petajoules thermal >90% load factor >50 years of production
Geothermal Power
MWth= m × (Hreservoir-H75°C)
Wairakei P
roduction
extensional fault
volcano-intrusion re
serv
oirs
< 3
km
dep
th
Geothermal Systems: Stored vs Flowing
liquid-‐dominated (100-‐300°C) vapor-‐dominated (220-‐250°C)
enthalpy kJ/kg 1000 2000 3000
sedimentary basin
reservoir
reservoir
reservoir
reservoir
Reservoir Heat Transfer-Idealized
Grant et al. 1982
seismicity
Photo: L Homer GNS Science
magmatism
Geothermal Energy
High temperature systems occur along plate boundaries, including: 1) mid-ocean ridges and continental rifts (Olkaria, Kenya; Aluto, Ethiopia) ; 2) ocean island (Hawaii, Iceland) and continental hot spots (Yellowstone, USA); 3) volcanic-magmatic arcs (Taupo Volc Zone, New Zealand, Sumatra & Java, Indonesia; Philippines; S. Kyushu, Japan; Central Mexico; El Salvador, Nicaragua, Costa Rica, Lardarello, Italy).
High Temperature Geothermal Resources: ~11,000 MWe installed; ~500-1500 active volcanoes
Conventional Geothermal Resource hot/warm springs
1 mm
reservoir
Hydrostatic P gradient & boiling point for depth T gradient in upflow zone at <2 km depth
Conventional Geothermal Resource hot/warm springs
1 mm
reservoir Reservoirs
220 to >300°C surrounded by cold rock hydraulically connected
>1017 J/km3 in rock
50-300 kg/s deep natural inflow
Hydrothermal System Lifespan 10,000 to >100,000 years
Broadlands-Ohaaki
Broadlands-Ohaaki
Energy in Fluid: Vapor versus liquid H2O
Critical Point: 374° C, 221 b Enthalpy (H): 2100 kilojoules/kg At 250° C Hwater=1086 kj/kg
Hvapor=2800 kj/kg
Energy in Fluid: Vapor versus liquid H2O
2800 kj/kg
Critical Point 374° C/ 221 b H ~2100 kj/kg
1086 kj/kg
Thain & Carey 2009 (Geothermics)
Cyclone Separator-Early Engineering Milestone Wells produce two-phase fluid: 25% steam & 75% water. Steam/water separation plants were a key innovation that allowed development of liquid-dominated reservoirs. This technology was proven with the development of the Wairakei resource.
Resource Assessment: Stored Thermal Energy T gradients in crust Boiling point for depth (hydrostatic pressure) is the max T gradient in high T systems Anomalous heat measured against normal gradient
boiling point for depth
Anomalous heat
for geothermal
Reservoirs
ΔQR heat stored in rock (J/m3) ΔQF heat stored in pore fluid (J/m3)
ΔQR = (1- Φ) ρP cR [Tz - Tz0] Φ porosity, ρP density, cR specific heat, Tz & Tz0 temperatures in & out
ΔQF = (Φ) ρL [hz - hz0] Φ porosity, ρL density, hz & hz0 enthalpies in & out
ΣQ = ΔQR + ΔQF Total Stored Heat Note sources of uncertainty:
reservoir volume (diffuse vs sharp boundary) reservoir temperature recoverable energy not considered
Physical: Heat & mass transfer Temperature-pressure gradients Permeability-porosity Hydrology & fluid flow
Chemical: Fluid compositions
Fluid-mineral equilibria Mineral corrosion/deposition Hydrothermal alteration
GEO
LOG
Y
Geothermal Energy
map: Reyes and Jongens, 2003
New Zealand Geothermal Energy Unique tectonic setting straddling a plate boundary. Extensional volcanic arc (10 mm/y) due to oblique subduction (North Island) Transpressional transform fault-Alpine Fault (South Island)
geothermal system andesite cone
White Island
Tongariro
Ruapehu
rhyolite caldera
Ngawha 25 MW
TVZ 890 MW
TVZ generation MW
Kawerau 147 Ohaaki 45 (114) Ngatamariki 82 Rotokawa 175 Mokai 111 Wairakei-Tauhara 330 (250+)
~15% NZ elec.
Geothermal Ro
wlan
d &
Sim
mon
s 201
2; G
eoph
ysics
imag
e: dip
ole-d
ipole
resis
tivity
(Stag
poole
& B
ibby,
1998
)
Extensional basin-volcanic arc
high heat flow volcanism, seismicity & hydrothermal activity
Structures segmented rift NE-SW
normal faults caldera volcanoes
Hydrothermal systems (red=low resistivity)
Compare the locations of volcanic
centers, faults, & hydrothermal systems
active caldera
active caldera
Wairakei
Taupo Volcanic Zone Geothermal Fields
Wairakei (>50 yrs) 25 km2 (reservoir 10 km2)
Hot springs & geysers in valley on northern edge
Fumaroles & steaming ground in the south
Borefield in between surface features.
Reservoir boundaries unknown when first drilled
Faulted volcanic stratigraphy Rosenberg et al. 2009 (Geothermics)
25 km2
Wairakei (>50 yrs)
50/150 wells (<2.5 km)
3 km3 fluid produced
2750 Petajoules
1450 kg/s
1130 kilojoules/kg
20 bar pressure drop
No injection Bixley et al. 2009 (Geothermics)
150 MW power station baseload operation >50 years
15 MW binary plant commissioned 2005
prawn farm: aquaculture
Wairakei: Next 50 Years
Total fluid production matches estimates of total pore fluid in reservoir, but exceeds natural flow rate. Production increases 1.7x this year.
No signs of reservoir degradation/cooling. Implies deep inflow has substantially increased as a result of production stimulation-unpredicted.
Additional 166 MWe was just commissioned. Numerical models forecast sustainable production for next 50 years.
*the F
uture
of G
eothe
rmal
Ener
gy: Im
pact
of En
hanc
ed G
eothe
rmal
Syste
ms
on th
e Unit
ed S
tates
in th
e 21st C
entur
y, Te
ster e
t al. 2
006
Blackwell & Richards 2004
Heat Flow Map
USA Resource Potential 14.0 x 106 EJ Stored thermal energy 3-10 km depth
0.28 x 106 EJ requires 2% Recovery 100 EJ Total consumption (2005)
EJ=1018 joules
San Andreas Fault System & Great Basin
Dorsey 2010
Geothermal = Project MWe
Geysers 850 Cerro Prieto 750 Salton Sea 410 Coso 302 Roosevelt 26 Steamboat Spgs 48 Mammoth 40 Beowawe 18 Dixie Valley 66 Raft River 13
no evidence of magmatic heat source
rese
rvoi
rs <
3 k
m d
epth
Geysers: Vapor-Dominated Reservoir
liquid-‐dominated (100-‐300°C) vapor-‐dominated (220-‐250°C)
enthalpy kJ/kg 1000 2000 3000
Great Basin
Dixie Valley
Beowawe Beowawe geyser, c. 1945
photo
: Whit
e, 19
92
First wells drilled 1959 Boiling point for depth to ~200 m
Temperature reversals at depth
Beowawe
Faulder et al 1997 Resource discovery drilled 1974
215°C @ 1200 to >2000 m depth Reservoir: Valmy Fm & Malpais fault damage zone
reservoir
Beowawe
Natural heat flow 17 MWth~230° C at 20 kg/s Resource permeability in fracture mesh in the hanging wall Deep thermal water-Pleistocene, dilute, bicarbonate-rich, alkaline pH Plume rises at an angle along basin bounding fault zone Power plant commissioned 1985; Reservoir volume <1 km3 Cool water inflow reduced production (later recovered) Modern production history 250-260 kg/s at ~215° C sustains ~17 MWe Total fluid production is 40% greater than reservoir resource Deep inflow stimulation likely
extensional fault
volcano-intrusion
rese
rvoi
rs <
3 k
m d
epth
Diversity of Conventional Resources
liquid-‐dominated (100-‐300°C) vapor-‐dominated (220-‐250°C)
enthalpy kJ/kg 1000 2000 3000
sedimentary basin
reservoir
reservoir
reservoir
reservoir
Engineered Geothermal Systems (EGS)
Deep hot rock
Induce fracture permeability
Inject fluid to advect thermal energy to surface
35 years of R&D (USA, Japan, Europe, Australia) 1.5 MWe plant Soults-sous-Forêts (France)
4 wells: 2 to 5 km depth, ~200°C
Temperature gradient: 40°C/km
Extensional tectonics: fracture connectivity restricted in granite basement (>1400 m depth)
Induced seismicity causes delays
Unconventional Resources
Enhanced/Engineered Geothermal Systems (EGS) Fenton Hill (USA) Rosemanowes (UK) Hijiori-Ogachi (Japan) Soults-sous-Forêts (France) Basel (Switzerland) Cooper Basin (Australia)
EGS Cooper Basin, Australia Prospect area 2000 km2
Hot granite (radiogenic heat) beneath 4 km sedimentary rk 4 wells: >4 km depth, whp 350 bar, >240°C Temperature gradient: ~60°C/km Horizontal compression: Flat fracture system-connectivity between wells 1 MW power plant commissioned 2012 Development suspended because of insufficient funds & excess supply
Steam flow Habanero 3 (March, 2008; Geodynamics Annual Report 2008)
Krafla, Iceland (50 MWe) volcanic eruption 1975-1984 intruded volume: 1 m wide
9 km long 7 km deep
erupted volume: 100x106 m3
temperature: >1100° C
Magmatic geothermal resources (unconventional)
Geothermal Energy: Sedimentary Basins
Raton Basin
Piceance Basin
Heat Transfer: Hybrid Applications
Piceance Basin
T gradient >40°C/km >250°C at 7 km 2 x 1017 J/km3
Hot rock volume >6000 km3
70 MWthermal/km3 for ~100 yrs Incentive for research
Geothermal Heat Transfer: Hybrid Applications
High demand for cooling & heating >300°C required Water demand Geothermal for preheating over long term Time span ~100 yrs
Piceance Basin
Heat Transfer: Hybrid Applications
Geothermal-Hydrocarbons
DoE-FORGE Frontier Observatory for Research in Geothermal Energy
(FORGE) Funding announcement for establishing & managing field lab Project comprises 3 Phases, with $31million allocated for I &
II. Main objective is site selection from a starting pool of 10. Phase I—12 mos; Phase II—12-24 mos; Phase III—60 mos EGI, U Utah is leading a consortium to recommend a site in
central Utah Ideal site: 175-225°C, 1.5 to 4 km depth, low permeability
(~10-16 m2), crystalline basement rocks Phase III includes drilling, stimulation, testing, using
innovative tools, methods, & supporting science/engineering
DoE-FORGE
DoE-FORGE
DoE-FORGE Phase I funding for full scale proposal Phase II funding supports geoscientific & environmental
investigations & proving site logistics Seismicity (natural/induced) are significant concerns Successful site selection will open new R&D opportunities for
engineers & scientists Diverse range of physical & chemical problems related to
engineering sustained heat & mass transfer for energy utilization largely involving water-rock interactions
Differs from unconventional oil & gas development, because energy flows need to be sustained & uniform for electricity production
Geothermal energy (heat from the Earth’s interior) is utilized for thermal energy and electrical energy production.
The resource is huge but low grade; the best/hottest resources are localized, dependent on geology.
Conventional hydrothermal resources have been in production for ~100 yrs; but long payback period + financial risks due to uncertainty in fluid flow systems & resource assessment.
Unconventional resources EGS-type resources are difficult to develop; i.e., how do you produce energy from a large volume (100-500 km3), hot “dry” rock at 3-5 km depth?
DOE FORGE represents new, big R&D support for an EGS field laboratory; new opportunity for advancing novel technologies. Utah test site is being proposed.
Summary